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What should Virginia drivers know about breath alcohol testing?

With many DUI arrests based on drivers’ breath alcohol test results, people should know how they work and what factors may affect their readings.

Each day, numerous people in Virginia are stopped, detained and arrested by law enforcement for driving under the influence and other alcohol-related offenses. In fact, the Virginia State Police report there were 21,308 DUI arrests across the state in 2018 alone. Many such arrests are based on the results of two different breath alcohol tests; however, most drivers do not understand how these devices work or what their legal rights are with regard to such devices.

How do BAC breath tests work?

Generally speaking, alcohol breath tests work by measuring the amount of alcohol that is found in the air that drivers breathe out of their lungs. When people drink alcohol, it first travels to the stomach and small intestine, where it is absorbed into the bloodstream and is then carried to other areas of the body, including the lungs. As people breathe, some of the alcohol that is racing through their system leaves the bloodstream through the tiny capillaries found in the lungs and is exhaled as they breathe. When officers wish to get an idea of how low or how high a person’s blood alcohol level is, the accused is often asked (or required in some circumstances) to blow into devices which are designed to use a sample of air taken from the lungs to measure the amount of alcohol in the bloodstream. The devices are designed to use the measurement of the alcohol in the breath sample to estimate drivers’ blood alcohol concentration levels at the time of the test. Readings of 0.08% or greater are considered over the legal limit, which may result in drivers getting arrested and charged with drunken driving or with other alcohol-related offenses.

What factors affect BAC levels?

Studies have shown that numerous factors may affect people’s BAC levels. In addition to the amount of alcohol they consumed, a person’s gender and weight can also impact their BAC level. For example, men generally have higher levels of a particular stomach enzyme which helps them break down and process alcohol at a faster rate than most women. Also, larger people often have more water in their bodies, which can help to either dilute the alcohol as it is absorbed into their bloodstreams or, simply disperse the alcohol throughout the body more effectively.

While it is a widely held belief that eating before drinking will help people process alcohol better, having a full stomach may actually help to absorb the alcohol in the stomach and hold it there which then can slow the processing of alcohol by the liver and result in them having a higher BAC level for a longer period of time.

How accurate are breath alcohol tests?

Generally speaking, the free market and the competition to provide accurate devices serves to help guarantee that breath testing machines work accurately although, there are numerous factors that may help to cause inaccurate readings. For example, some handheld devices may give false positives as a result of needing a charge or to have their batteries changed out. Further, improper calibration, or the failure to properly recalibrate the machines by someone who has the appropriate training, may also cause inaccurate results.

In addition to issues relating to the devices themselves, specific factors relating to the person providing the breath sample and environmental factors may also affect breath test readings. Some studies have suggested that periods of stress (like an encounter with law enforcement) can increase the rate of circulation and breathing, thus contributing to “higher” readings. There also some evidence that using mouthwash, breath fresheners or other products containing alcohol immediately prior to testing may give a false positive, and so too may taking a drink of an alcoholic beverage within 15 minutes of giving a breath sample as it may leave trace amounts of alcohol in people’s mouths.

Do I have to take a breath test offered to me by a police officer?

Generally, breath testing is done by the use of two different devices. Often, police officers will use a Preliminary Breath Test (PBT) to check blood alcohol levels in the field. These devices are HANDHELD and will usually be offered prior to arrest. Under current Virginia Law (as of 1/1/2020), persons are NOT required to take these handheld tests and should NEVER do so regardless of what the police officer tells them. This is true whether the person is detained on suspicion of DUI, Underage Possession of Alcohol , Appearing Drunk in Public or any other type of alcohol offense.

The other type of device used by law enforcement is the large, tabletop testing device which is kept at most jails and which is used almost exclusively for DUI investigations. These devices are far more accurate than their handheld cousins and IF A POLICE OFFICER INSTRUCTS YOU THAT YOU MUST TAKE THIS TEST IN REFERENCE TO AN ARREST FOR A DUI, THEN YOU SHOULD DO SO. Failure to take the tabletop test at the jail will probably result in additional criminal charges and the loss of driving privileges.

If you have other questions about the use of breath testing devices or your legal rights about whether or not you can or should take such a test, you should consult with an attorney who is knowledgeable in such matters.